Method and apparatus for gas lifting fluid from plural zones of production in a well



Dec. 15, 1959 R. c. DAVIS ETAL 2,917,004

METHOD AND APPARATUS FOR GAS LIFTING FLUID FROM PLURAL ZONES OF PRODUCTION IN A WELL Filed April 30. 1954 6 Sheets-Sheet 1 Ray 6. Davis Phi/lip E. Pierce INVENTORS v Z0 t q BY Mam A T TORNEYS 1959 R. c. DAVIS ETAL 2,917,004

METHOD AND APPARATUS FOR GAS LIFTING FLUID FROM PLURAL ZONES OF PRODUCTION IN A WELL Filed April 30 6 Sheets-Sheet 2 INVENTORS A TTORNFTYS Roy 6. Davis Phillip E Pie/6e IS ETAL GAS LIFTING FLUID FROM PLURAL ZONES OF PRODUCTION IN A WELL Filed April 30. 1954 6 Sheets-Sheet 3 Dec. 15, 1959 R. c. DAV

METHOD AND APPARATUS FOR IN V EN TORS pwfi Roy C. Davis Phi/lip E. Pierce 310% /3' ATTORNEYS W T i I WE Dec. 15, 1959 R. c. DAVIS ETAL 2,917,004

METHOD AND APPARATUS FOR GAS 1.1mm: FLUID FROM PLURAL ZONES OF PRODUCTION IN A WELL Flled April 30 1954 6 Sheets-Sheet 4 Roy 0. Davis Phi/lip E. Pierce 0 O QL M w A TTORNEYS Dec. 15,1959 R. c. DAVIS ETAL 2,917,004

METHOD AND APPARATUS FOR GAS LIF'TING FLUID FROM PLURAL zomzs OF PRODUCTION IN A WELL A TTORNEYS Dec. 15, 1959 R. c. DAVIS ETAL 2,917,004

METHOD AND APPARATUS FOR GAS LIFTING FLUID FROM PLURAL ZONES OF PRODUCTION IN A WELL Filed April 30. 1954 6 Sheets-Sheet 6 Roy 62 Davis Phi/lip E. Pierce INVENTORS.

ATTORNEYS United States Patent Ofiice 2,917,004 Patented Dec. 15, 1959 METHOD AND APPARATUS FOR GAS LIFTING FLUID FROM PLURAL ZONES F PRODUCTION IN A. WELL Application April 30, 1954, Serial No. 426,734

32 Claims. (Cl. 103-233) This invention is concerned with a method and apparatus for removing fluid from a well by gas lift, and is particularly concerned with method and apparatus for removing fluid by gas lift from separate zones of production in a single well.

Heretofore, gas lift installations for producing fluid from separate zones of production have been, to a large extent, impractical and uneconomical due to the fact that such installations required cumbersome and costly equipment and a multiplicity of parts resulting in much expenditure in time, labor and equipment in installation and removal.

Furthermore, such prior practice has failed to provide means for accurately measuring the volume of gas used in the production of the separate zones and has further resulted in the wastage of gas. Also, such prior installations have failed to accurately measure produced formation gas from each separate zone.

State regulatory bodies desire that a reasonably accurate record he kept of the volume of gas injected to produce each zone and the volume of gas produced from each zone in consideration of conservation laws. Gas has become increasingly more valuable, thus requiring that the use thereof be controlled, not only in the interest of conservation, but in the interest of economy.

In order to meet the requirement of measuring the injected gas for the production of separate zones in a well, it was necessary, prior to the present invention, to install a separate gas passage for each zone, separately controlled, a separate eductor tube for each zone, and two sets of flow valves, each set being operated separately and independently by gas pressure from one of the separate gas passages. In order to install such a system, it was necessary to provide complicated packers between the separate pipes extending into the well, and such systems were unwieldly and complicated and diflicult to install. The gas passages were necessarily small in cross section due to limited space in the well, thereby providing an insuficient volume for injection gas storage. The cost of installation of such system made it prohibitive, and in most instances it would be cheaper to drill another well to produce the second zone than to install such a system.

Furthermore, it is desirable and necessary that the gas lift valves employed in the production of each separate zone in a multiple zone completed well be controlled from the surface so that the volume of gas injected may be accurately controlled, and so that the surface control equipment may be regulated in order to meet the changing conditions of the formations and in order to comply with the allowable production set by state regulatory bodies.

Heretofore, the industry has been able to control and regulate one zone of production by use of surface controlled flow valve, but they have found it necessary to use automatic or differential type valves for the production of another zone in the same well, because of the difference of productivity of the separate zones, requiring difierent frequencies of gas injection.

The differential or automatic valve depends solely upon the predetermined relation between the pressure of the injected gas and the pressure head of the fluid to be ejected.

In the employment of dilierential type valves it is not possible to accurately control the action of such valves, or the production of the zone with which such valves are used, by means of surface control equipment. Therefore, no surface adjustment can be made in the production of the zone which is produced by dilferential valves where the two strings of valves have a common gas passage for injection, and the second zone is produced by surface controlled pressure operated valves.

It has also been practiced in the past in the completion of wells to gas lift oil from separate zones of production to provide a separate string of valves attached to and communicating with each eductor tube provided for each zone of production, the valves in one of which strings are differential type valves, as mentioned. above. It has been the practice to provide a plurality of valves on each eductor tube at spaced intervals along its length in order to unload the well of fluid down to the working valve, which is usually the lowermost valve on the string. The valves are set to open at graduated pressures down the hole with the uppermost valve being set at the highest pressure, and the valves are successively uncovered as the fluid in the annulus about the eductor tube is ejected through the valves and upwardly through the eductor tube.

In some instances such plural eductors have been run in parallel relationship, requiring that they be clamped together by clumsy and complicated arrangements, and requiring complicated packer elements in order to separate the different zones. In other instances one eductor tube has been concentrically mounted inside of the other with the valves for each eductor carried on the outer eductor tube and requiring a cross-over connection in conjunction with each of the valves communicating with the inner eductor, thus multiplying the make-up joints required in the installation of such system.

In still other instances an eductor tube has been run inside another pipe and the annulus between them served as a common gas supply reservoir. Pressure operated valves were placed inside the outer pipe to lift fluid in the casing annulus, and differential valves were placed on the inner eductor to lift fluid to the inner eductor. This system was unsatisfactory because of insuflicient volume of injection gas storage resulting in low lifting capacity. Furthermore, the usual well requiring gas lift does not produce enough fluid to be efficiently and economically lifted in the enlarged casing annulus due to wastage of gas by slippage and due to the large volume of gas required to produce through the casing.

In our invention all of the foregoing undesirable practices have been overcome. In our method and apparatus separate eductors are provided for separate zones of production in a well, with a full set of surface controlled pressure operated valves for injection of gas into one eductor and a single surface controlled pressure operated valve for the injection of gas into the other eductor. A common gas injection passage is provided for the separate eductors. The well may be unloaded of fluid through one of the eductors by reversing the flow through the other eductor, and each zone may be produced separately through its respective eductor employing surface controls, permitting the adjustment and regulation of the amount of gas injected for production of each zone, the measurement of the amount of gas injected for the production of each zone, and the regulation of production from each zone of production.

A primary object of this invention is to provide a separate zones'of production in an oil well in which the valves used to produce the separate zones can-be positively controlled from the surface, permitting the adjustment of surface control equipment to conserve gas and to produce each separate zone at rates prescribed by regulatory bodies in the interest of conservation.

Another important object of this invention is to provide a method and apparatus for the gas lift production I of oil from multiple zones of production in an oil well whereby the volume of gas injected for the production of each zone can'be accurately measured and the volume of gas produced from each zone can be accurately measured.

A stillfurther object of this invention is to provide a method and apparatus for the gas lift production of oil from multiple zones of production in an oil Well wherein one full string of conventional surface controlled fiow valves are employed to produce one zone and one conventional surface control valve is employed to pro duce another zone, thereby drastically reducing the number of valves required and the number of parts and connections required. in making the installation of such a system.

Another important object of this invention is to provide a method and apparatus for gas lifting oil from multiple zones of production in a well whereby the well may be unloaded of fluid by placing the eductor tubes for the separate zone into communication and unloading the well through one of the eductor tubes.

Another object of this invention is to provide a method and apparatus for gas lifting fluid from multiple zones of production; in a-well wherein a common gas reservoir is. provided for supplying injection gas to the separate.

eductorsthroughsurface controlled pressure operated valves.

A still further object-of this invention. is tofprovide; a method and apparatus-for gas -lifting'oil' from multiple.

zones of production; in a well which reducesthe cost ofinstallation; reduces the amount of gas required in production and makes possible the economical production of plural zones of production in a single well.

An additional object of this invention is to provide a method and apparatus of producing fiuid from multiple zones of production in a well wherein gas produced from one zone may be employed to gas lift fluid from other zones in the same well.

Other and further objects and advantages of-our in-. vention willvbecome apparent upon reading the detailed specification hereinafter following, and by referring to the drawings annexed hereto.

Suitable embodiments for carrying out our invention are shown in the attached drawings wherein:

Fig. I is a diagrammatic view of one form of in! stallation of our gas lift system and apparatus in con-. nection with a well having two zones of production.

Fig. II is a cross-sectional elevational view of a typical push-down to close motor valve used in the installation and operation of our gas lift system.

Fig. III is a cross-sectional elevational view of a typical push-down to open motor valve used in the installation and operation of our gas lift system.

Fig. IV is a diagrammatic view of a modified form of down-hole installation for our gas lift system employed in a well having two zones of production.

Fig. V is a diagrammatic view of another form of installation of our gas lift system'and apparatus in a well having two zones of production.

Fig. VI is a fragmentary cross-sectional elevational view of a typical valve mandrel with a pressure-operated valve and a back flow check valve mounted in connection therewith.

Fig. VII is a cross-sectional view taken along line VII-VII of Fig. VI.

ffig. VIII is a cross-sectional elevational view ofa. typicalcross-over mandrel used with ourinvention, ShQW- .5, said nipple having a lateral cross-over passage 35 ing typical slip joints carried therein, and with a typical pressure-operated flow valve carried thereon.

Fig. IX is a cross-sectional view taken along the line IXIX of Fig. VIII.

Fig. X is a cross-sectional view taken along the line XX of Fig. VIII.

Fig. XI is a cross-sectional elevational view of a typi- -valve carried thereon.

Fig XV is a cross-sectional elevational view of a typical cross-over mandrel connected to the modified valve mandrel shown in Fig. XIV, said cross-over mandrel having typical slip joints disposed therein connected with the inner eductor.

Fig. XVI isa cross-sectional elevational view of a typical through-flow fitting used with our invention having a typical slip joint disposed therein with lateral ilowpassages through the-wall of the fitting above the slip joint.

Fig. XVII is a diagrammatic view of another form installation of our system of gas lifting from multiple zones ofproduction' wherein the injection gas is taken from one ofthe zones of production in the well.

In the drawings, numeral references are employed to designate thevarious parts, and like numerals designate like parts throughout the various figures of the drawings.

Referring to Fig. I, the numeral l'indicates a weft-note extending-verticallyinto'theearthsstrata. A well casing 2' extends intothe well bore and beyond the zones of production Sand 10;

The zone of production 3 communicates with the interior of the casing 2 through the perforations 4 in the wall of thewell casing.

A tubing string 5, constituting an eductor for thelower zone 10, extends into the casing 2 and the casing is closed about the tubing atthe upper end by means of a suitable well head 6. The annular space between the tubing and the casing is indicated bythe numeral 7, such annular space forming a common gas'reservoir for injection of gas for gas lifting fluid from the zones of production 3 and- 10, as will be explained later.

Anupper packer 8 is carried by tubing string 5 and-is arranged in theannular space 7 between the casing 2 and the tubing 5 for the purpose of sealing off the annular space 7-between the casing-2and the tubing 5, thus seal- 7 ing ofi-theannular space-above the upper zone of production 3.

Another packer-9 is carried by tubing string 5 and is arranged between the tubing 5- and the casing Zfor the purpose of sealing off the annular space '7 between the upper zone 3 and thelower zone 10. Suitable perforations ll-areprovided in the wall of casing 2 to allow cornmunication between the interior of the casing and the lower-zone 10.

A- perforated tailpipe12- is attached to the lower end ofthe tubing string 5- and extends into the chamber 13 formed-by the lower end of thewell bore and the patker 9.. The perforated tail pipe ll permits-the ilow of i" from the lower formation 10 into the interior of the tubing eductor 5.

A chamber 14 is-also formed in casing 2 between the packers 8 and 9.

A cross-overnipple i6 is connected in the tubing string (of which there may be-a plurality)extending through wall thereof said passage communicating with the inthe.

terior of the connector pipe 26 and eductor tube 31, so that fluid from the upper zone 3 may enter the eductor tube 31 through the passage 15 and connector pipe 26.

An upwardly facing slip joint receptacle 17 is provided as a part of the nipple 16 and extends above the passage 15, and a vertical passageway 18 is provided about the slip joint receptacle 17 for the purpose of permitting fluid which enters the tubing string 5 to pass upwardly about said slip joint receptacle 17. The detailed construction of the nipple 16 and slip joint receptacle 17 is shown in Figs. XII and XllI, and will be hereinafter described.

A cross-over mandrel 20 is attached as a part of the tubing string 5. Said cross-over mandrel 20 has a central longitudinal passage 19 therethrough to permit the flow of fluid therethrough and through the eductor tube 31.

A downwardly facing slip joint receptacle 21 is provided in the lower end of the cross-over mandrel 20 and an upwardly facing slip joint receptacle 22 is provided in the upper end of the crossover mandrel 20.

A plurality of spiders 23 are spaced about the upper and lower ends of the cross-over mandrel 21), such spiders 23 being spaced apart to provide longitudinal passages 24 for the flow of fluid about the slip joint receptacles 21 and 22 and through the tubing string 5.

A lateral port 25 extends from the inner bore 19 of the crossover mandrel 20 and is arranged to communicate with the casing annulus 7 through the flow valve 30, when said flow valve is open, thereby permitting the flow of fluid to and from the casing annulus through the bore of the eductor tube 31.

A section of pipe 26, which forms a part of the eductor 31, extends between the cross-over mandrel 20 and the slip joint receptacle 17. A slip joint 27 is attached to the lower end of the pipe 26, such slip joint being frictionally engaged in the slip joint receptacle 17. Such slip joint 27 carries sealing elements thereon and has a longitudinal flow passage therethough to permit the flow of fluid into and through the eductor tube 31. A like slip joint 28 is provided on the upper end of the pipe 26, such slip joint being frictionally inserted in the slip joint receptacle 21. These slip joints are shown and described in detail hereinafter.

A suitable base 29 is mounted on the outer side of the tubing string 5 and has a passage therethrough communicating with the lateral port 25. A suitable pressureloaded surface controlled flow valve 30 is carried in the base 29 and is arranged to control the flow of fluid through the port 25 to and from the eductor 31.

The pressure loaded surface controlled flow valve 30 may take the form of a variety of such valves now offered to the trade. A suitable form of such valve is illustrated and described in detail hereinafter.

It is to be noted that there is no backflow check valve mounted in connection with the flow valve 30, the purpose of which will be hereinafter explained.

The inner eductor 31 extends concentrically through the tubing string 5 and communicates with the upper zone of production 3 through the port 15, slip joint 27, slip joint 21., cross-over mandrel 20 and slip joint 32. Slip joint 32 is carried on the lower end of the upper section of the eductor 31 and is frictionally engaged in the upwardly facing slip joint receptacle 22.

The upper end of the eductor tube 31 extends through a suitable head nipple 33 arranged on the well head.

A plurality of pressure-loaded surface controlled flow valves 40 are mounted on the outer side of the tubing string 5 and are arranged to communicate with the interior of the tubing, when open. Suitable bases 42, each having a flow passage therethrough communicating with suitable lateral passages 43 leading into the tubing string 5, are mounted at spaced intervals along the tubing. A back pressure check valve 41 is mounted between each of the valves 40 and the respective bases 42 therefor. The back pressure check valves 41 permit the flow of fluid from the casing annulus 7 through the valves 40 into the tubing 5 but prevents the flow of fluid from the tubing into the casing annulus.

The valves 40 are customarily pressure-loaded at graduated pressures down the tubing, the uppermost valve being loaded at the highest pressure, in a manner already well known in the art. Such arrangement is for the purpose of unloading the well of fluid down to the working valve, which is customarily the lowermost valve in the string. As is well known in the art, the well is usually filled with liquid while the well is being worked. over or prior to putting it in production, in order to provide a pressure head to confine the pressures existent in the producing formations. After installation of the string of valves 40, pressure is built up in the casing annulus suflicient to force fluid from the casing annulus through the valves into the tubing and out of the well. Liquid is ejected through each of the successive valves down the hole as the liquid level is lowered, until the liquid in the casing annulus has been lowered to thelowermost working valve, at which time the pressure can be lowered to permit the upper valves to close and gas can be injected at the opening pressure of the working valve for production. This is a practice well known in the art.

A by-pass line 35 is provided between the casing annulus 7 and the inner eductor 31. A manually operated valve 36 is arranged in the bypass line 35 for the purpose of controlling communication between the casing annulus 7 and the eductor tube 31. The valve 36 normally remains closed except during the unloading of the well of liquid, which operation will be explained hereinafter.

A flow line 38 extends from the eductor tube 31 to the separator 37, the flow through such flow line being controlled by the manually operated valve 39. The separator 37 receives liquid and gas produced from the upper zone of production 3 through the eductor tube 31. The

lighter gas flows out of the separator through gas line 56 and through a recording flow meter 57 which measures and records the gas ejected through the eductor tube 31. A liquid line 55 extends from the lower end of the separator 37 and carries liquid produced through eductor 31 to a suitable storage tank (not shown).

A by-pass line 45 extends from the line 35 into the tubing string 5, the flow of fluid throughsaid by-pass line 45 being controlled by the motor valve 46. The valve member in motor valve 46 is actuated by a suitable diaphragm 47.

A flow line 49 is arranged between the interior of the tubing string 5 and the separator 48. The separator 48 is provided for the purpose of separating the gas and oil produced through the tubing string 5. A motor valve 50 controls the flow of fluid through the flow line 49, such motor valve 50 being controlled by suitable diaphragm 51.

A liquid line 52 extends from the lower part of the separator 48 to a suitable storage tank (not shown). Gas accumulated in the separator 48 flows through the gas line 53 and through the flow meter 54, such flow meter being provided for the purpose of measuring the amount of gas ejected through the tubing string 5.

A gas injection line 60 is provided to communicate with the casing annulus 7 for the purpose of injecting gas into the casing annulus for the opening of the tubing valves 40, and the inner eductor valve 3%, so as to &

inject gas under pressure into the tubing string 5 and into the inner eductor 31 for the purpose of unloading the well of liquid and for gas lifting fluid from the productive formations 3 and 10, all in the manner which will be hereinafter described.

A gas conduit 61 communicates with the injection line 60 and with a source of gas under pressure (not shown). A motor valve 62 is positioned in the conduit 61 for the purpose of controlling the flow of gas through such conduit, the valve member in said motor valve being actuated by a suitable diaphragm 63.

The operation of the motor valve 62 is, automatically controlled by a suitable control device 64 of conventional construction. The motor valve 62 may be opened and closed at, predetermined intervals by the settingof'the control device.

The gas injected through the conduit 61 is measured and recorded by a suitable recording flow meter 65 so that the volume of gas injected for the production of oil from the lower zone 10 may be measured and regulated.

A gas line 66 also communicates with the injection line 60 and with a source of gas under pressure (not shown). The flow of. gas through the line 66 is controlled by a motor valve67, the valve member in which valve is controlled by a diaphragm 68. The valve 67 is automatically opened and closed at predetermined intervals by a conventional control device 69, and the volume of gas passing through the line 66 is measured and recorded by a recording fiowmeter 70. The meter 70 measures and records the volume of gas injected for the production of fluid fromthe upper zone of production 3.

A manifclded control line 71 is connected between the diaphragms of motor valves 46, 50 and 67 and control device 69 for the purpose of simultaneously operating these valves through the common control device 69. The manifold line 71 communicates with the upper sides of the diaphragms of each of the motor valves 46, t) and 67 and with the time control device 69, whereby the time control device 69 will simultaneously operate all three of such valves. Motor valves 46 and 67 are push down to close valves, whereas motor valve 5% is a push down to open valve, so that when motor valves 46 and 67 are onen, motor valve 50 is closed, and when motor valve 50 is open, motor valves 46and- 67 are closed.

Fig. II shows a cross-sectional elevational view of a typical push down to close motor valve used with our invention. In such valve a chamber 72 is provided having a flexible diaphragm 73 dividing it transversely. A valve stem 74 is attached to the lower side of the diaphragm 72, such valve stem having a valve head 75 thereon which controls the flow of fluid through the valve seat 76 and through the inlet and outlet lines 78 and 77, respectively. Gas pressure entering the control line 71 (or any other control line to which it is con nected) pushes the diaphragm 73 downward to close the passage through the valve seat 76. Gas pressure is admitted to the control line 71 by a control device such as shown at 69 at predetermined intervals, depending upon the setting of the control device. The motor valve shown in Fig. II is typical of the motor valves 46 and 67 shown diagrammatically in Fig. I, and is typical of all other push down to'close motor valves used in our system.

Fig. III shows a cross-sectional elevational' viewofa typical push down to open motor valve and is typical ofthe motor valve 50 shown diagrammatically in Fig. I, and of all other push down to open motor valves e.. ployed herein.

In Fig. III a chamber 79 is transversely divided by a flexible diaphragm 80. A valve stem 81 is attached to the lower side of the diaphragm 80 and hasa valve head 82 thereon which controls the flow of fluid through the opening in the valve seat 33 and through the inlet line 86 and outlet line 85. The valve head 82 is normally held in engagement with the valve seat 83 by the spring 84, but when sufiicient pressure is admitted through the line 71 to the upper face of the diaphragm 80 to overcome the spring 84, the valve head 32 is pushed away our gas lift system wherein the eductor tube 31 and its.

extension 94 communicates with the lower zone of production 1t) and the tubing eductor 5 communicates with the upper zone of production 3. This installation is desirable where the lower zone has a higher productive capacity than the upper zone. In Fig. I the upper zone has a higher productive capacity than the lower zone. The eductor 31 is preferably placed in communication with the productive zone having the higher productive capacity, thereby requiring less frequent injections of lifting gas at higher pressure, as will be explained.

In the installation shown in Fig. IV a through flow fitting 90 is attached as a part of the tubing string 5. Such through flow fitting 96 has a longitudinal passage 92 therethrough for the purpose of permitting the flow of fluid from the lower zone 10 through such fitting and into the connector pipe 94 and eductor tube 31. An an nular partition 91 is made a part of through flow fitting 90 and prevents the flow of fluid into the tubing string 5 about such fitting from the lower zone 10. An upwardly facing slip joint receptacle 93 is provided in the fitting 90. A length of pipe 94 is arranged between the fitting 9t} and the cross-over mandrel 20, such crossover mandrel 20 being the same in construction as the cross-over mandrel shown in Fig. I. In Fig. IV the crossover mandrel 20 is positioned higher along the tubing string 5 than its position in Fig. I.

A slip joint 95, which is of the same construction as the typical slip joints hereinafter described in detail, is attached to the lower end of the length of pipe 94 and is frictionally engaged in the slip joint receptacle 93. Another such slip joint 96, of like construction, is attached to the upper end of pipe 94 and is likewise frictionally engaged in the slip joint receptacle 21 in the lower end of the cross-over mandrel 2%.

A plurality of perforations or side ports 97 are provided through the wall of the tubing string 5 abovev the partition 91, such perforations permitting the passage of fluid from the upper zone 3 into the tubing eductor 5.

In Fig. V is shown another modified form of installation wherein the valve 3% and cross-over mandrel 20 and the valves 40 are arranged in the same relationship with respect to the eductor tube 31 and the. tubing eductor 5 as in Fig. I. .The valve 30 communicates with the eductor 31and controls production from the upper zone 3 and valves 49 communicate with and control pro-. duction from the lower zone 1%. However, in such installation an additional surface controlled flow valve 99, of the same type as flow valves 30 and 40, communicates with the eductor tube 31 and upper zone 3 through a typicalcross-over mandrel 29a. It will be observed that a back-flow check valve 109 is interposed between the flow valve 99 and the passage 98 leading into the cross-over mandrel, such flow valve preventing the back how of fluid from the eductor 31 into the casing annulus 7.

A connector pipe 101 extends between the upper and lower cross-over mandrels 2i! and 29a such connector pipe 101 having a typical slip joint 105 at the upper end thereof which is frictionally engaged in the downwardly facing slip joint receptacle in the upper cross-over mandrel 20, and the lower end of such connector pipe has a typical slip joint 106 frictionally engaged in the upwardly facing slip joint receptacle in the lower crossover mandrel Zita.

In Fig. V a push down to close motor valve 102 is substituted for the manually operated valve 36 of Fig. I, and a push down to open motor valve 103 is substituted for the manually operated valve 39 of Fig. I. A manifolded control line 194 inter-connects the diaphragms of motor valves 192, 103 and 62 and control device 64, so that said motor valves may be actuated simultaneously by the common control device 6 Therefore, when motor valves 62 andllll are open, motor valve 103 is closed, andvice versa.

In Figs. VI and VII is shown a typical valve mandrel which is arranged for attachment as a part of the tubing string for mounting a suitable pressure-loaded flow valve for communication with the interior of the tubing eductor 5. The flow valves 40 and check valves 41 are mounted in the tubing string by means of such typical mandrel. The body of the valve mandrel, so shown, is indicated at 108 and such valve mandrel is shown to be threadedly engaged at its lower end with the typical cross-over mandrel 20, as indicated at 109. In an actual installation the valve mandrel 108 may be spaced from the cross-over mandrel by one or more joints of the tubing string 5. The eductor tube 31 extends concentrically through the valve mandrel 108.

The pressure-loaded valve employed with our invention may be any suitable valve of this type, of which there are several. A suitable form of such valve is shown and described herein. The valve as shown comprised of a housing 110 which is divided into two parts by a partition 111, forming a dome portion 112 which is filled with a predetermined charge of gas under pressure and sealed by a threaded plug 122. A bellows diaphragm 113 is attached to, and extends below, the partition 111 and the interior of such diaphragm communicates with the dome portion through a passage 114 in the partition so that the interior of the bellows is charged with the same pressure as the dome portion 112. A valve stem 115 is attached to, and extends below, the bellows diaphragm 113, such valve stem having a valve head 116 thereon which controls the flow of fluid through the passage in the valve seat 117. A flow passage 118 is provided through the valve base 119 and such valve base is threadedly engaged in the mounting base 29 (Fig. VIII) or check valve 41 (Fig. VI), so that the passage 118 communicates through the passage or 43 in the mounting bases 29 or 42 with the interior of the eductor tube 31 or the interior of the tubing eductor 5, as the case may be.

Lateral side ports 120 are provided through the valve housing 110 so that fluid under pressure from the casing annulus 7 may enter through such ports 120 and upon increase of such pressure above the predetermined pressure charge in the dome 112 and diaphragm 113 the diaphragm will contact and lift the valve head 116 Oil of the seat 117, thereby opening the valve. The valve is normally closed by the pressure therein, and is opened by injection of gas pressure into the casing annulus to a sufficient value to overcome the pressure charge in the valve. Thus such a valve may be controlled entirely from the surface by the injection of gas under pressure. Such valve is typical of all the pressure-loaded surface controlled valves employed with this invention. l

It is to be noted in Fig. VI that a check valve 41 is interposed between the pressure loaded valve 40 and the valve base 42 whereas in Fig. VIII no such check valve is employed between the valve and base 29. A check valve is mounted in connection with the valves 40, which communicate with the tubing string eductor 5, but no check valve is used in connection with the valve 30 which communicates with the inner eductor 31.

Any suitable form of back flow check valve may be employed. However, a typical check valve 41 has been illustrated in Fig. VI. Such check valve has a body 125 with a spring-urged valve member 126 moveable therein. The valve member 126 controls the flow of fluid through the opening in the seat 127. Side ports 128 are provided through the side of the valve member 126 to permit the flow of fluid through the valve member when the valve member is pushed away from the seat 127. A passage 129 is provided through the upper portion of the check valve 41, communicating with the passage 118 in the valve base 119, and a passage 130 is provided in the lower part of check valve body 125, such passage being in communication with a passage 131, in the valve base 42. The passage 131 communicates with the interior of the tubing eductor 5 through the lateral pas"; sage 43; The check valve 41 permits the flow of fluid into the tubing through valve 40 but prevents the flow of fluid in reverse direction through the valve 40.

A cross-over mandrel 20, which is typical of all crossover mandrels indicated herein with typical forms of slip joints inserted therein, and a typical pressure loaded valve 30 communicating with the interior of the cross-over mandrel are illustrated in detail in Figs. VIII, IX and X. In such figures both of the slip joints 28 and 32 are of identical construction and, a description of one of said slip joints will suflice for both. All slip joints indicated herein are identical in construction to that hereinafter described.

The typical slip joint has a' tubular body portion 135, having an enlarged head 136 thereon. The head 136 has a beveled shoulder 137 thereon which is arranged to contact a complementary beveled shoulder 138 on the spiders 23 when the slip joint is inserted in the slip joint receptacle 21 or 22. The head 136 on the upper slip joint 32 is threadedly engaged with the eductor tube 31, as indicated at 139, and the tubular body of the slip joint is engaged with the head 136 by threaded engagement, indicated at 140. A plurality of annular packing rings 141 are disposed about the tubular body 1.35, said packing rings being held in spaced relation on the body 135 by means of spacer elements 134.

The head 136 of the lower slip joint 28 is threadedly engaged with the section 26 of the inner eductor 31 by means of threads indicated at 142.

The Slip joints 28 and 32 are frictionally engaged within the receptacles 21 and 22, respectively, provided at the opposite ends of the cross-over mandrel 20, and the sealing elements 141 prevent the flow of fluid about the bodies 135 of the slip joints. However, fluid may flow through the bores of said slip joints so that fluid may pass from the productive zone with which the eductor 31 is in communication, and fluid may pass through valve 30, to or from eductor 31.

The cross-over mandrel 20 is provided with passages 24 extending longitudinally therethrough about the slip joint receptacles 21 and 22 and between the spiders 23 so that fluid may pass upwardly through said passages 24 from the productive formation with which the tubing string 5 is in communication.

The pressure-loaded valve 30 is mounted on the crossover mandrel 20, and is arranged to communicate with the interior of the mandrel 20 and with the eductor tube 31 through the lateral passage 25, so that when said valve 30 is opened by sufi'icient pressure in the casing annulus, gas may be injected into the inner eductor 31 to lift the fluid produced from the formation with which the eductor 31 communicates.

The slip joints 28 and 32 effectively separate the interior of the tubing eductor 5 from the interior of the eductor tube 31, preventing the intermingling of fluid from the separate zones of production, and at the same time permits the injection of gas under pressure to the eductor 31. The slip joint arrangement also permits the eductor 31 to be set in the cross-over mandrel 20, after the tubing has been run into the well, and eliminates a multiplicity of make-up joints.

Fig. XI shows a packer which is typical of the packers 8 and 9 shown schematically in Figs. I, IV, V and XVII, for separating and sealing off the zones of production in the well.

Other forms of production packers could be used, Fig. XI shows a suitable form.

A coupling nipple 143 connects the cross-over mandrel 20 with the inner sleeve 145 of the packer, such nipple being threadedly engaged at 144 with the lower end of the cross-over mandrel and threadedly engaged at 146 with the upper end of the packer sleeve 145. However, it

is to be understood that, in an actual installation, the

11 cro ss-oyer'mandrel 20 and the packer 8 may 'bespaced apart by one or more sections oftubing string 5.

The flexible reinforced packer cups 147, made of resilient material, are disposed about the inner sleeve 145, such cups being turned in opposite directions and arranged to sealin'gly engage the inner wall of the casing 2. Each of the packer cups 147 has a supporting bushing 148, molded thereto, and a plurality 'of reinforcing wiresi49 molded in the body thereof-for the purpose of flexibly supportingsame. The'oppositely turned supporting thimbles 159 are disposed about the sleeve 145' and support the cups 147. The spacer sleeves 151 are arranged about the packer sleeve 145 and-are engaged with the bushings T48 and the couplings 143- and 152 for the purpose of spacingand preventing longitudinal movement of the packer cups on the sleeve 145.

The coupling 152 connects the lower end of the packer sleeve 145 with cross-over nipple 16. The coupling 152 is threadedly engaged with the sleeve 145, as indicated at 153, and the lower end of said coupling 152 is threadedly engaged with the cross-over nipple 16 bythreads indicated at 154. In actual practice one or more sections of tubing string may be interposed between packer 8 and cross-over nipple 16.

The section of pipe 26 which 'communicates'with eductor tube 31, passes through the packer sleeve 145 and is connected at its lower end to the slip joint 27' by means of threads indicated at 155. The slip joint 27 is the same in construction as the typical slip joints previously described, and is frictionally engaged in the upwardly facing slip joint receptacle 17, in the cross-over nipple 16, the detailed construction of which cross-over nipple and slip joint receptacle is shown in Figs; Xil and XIII.

The slip joint receptacle i7 156 with spiders 157 arranged at the upper end thereof, said spiders being spaced apart to provide flow passages 18 thereabout. The spiders 157 have beveled shoulders 158 on the upper side thereof with which the beveled shoulder 137 on the slip joint 27 comes into contact to limit the downward movement of the slip joint in the receptacle E7. The inner bore 156 of the slip joint receptacle is closed at its lower end by a plug 159. The lateral passages 15 through the wall of the crossover nipple 16 permit the flow of fluid from the productive formation 3 into the inner eductor 31, and thehpassages 18 are provided about the lateral ports 15, the siip joint receptacle 17 and between the spiders 157 so that fluid entering the tubing eductor 5 from the lower formation may pass upwardly through saidv passages 18 and through the tubing 5.

The packer 9 (shown diagrammatically in Figs. 1, IV,

V and XVII) is carried about the tubing 5 below the has arr-inner bore portion cross-over nipple 16 and separates the productive forma- V tions 3 and it). Said packer 9 is not illustrated in Fig. XII, it being the same in construction and mounting as the typical packer 8, illustrated in Fig. XI. 'It will be seen that the slip joint receptacle and slip joint construction shown in Figs. X11 and XTII, with the side ports 15, permits fluid from the separate zones 3 and 16 to be separated and produced through their respective eductors 3i and 5, and prevents the intermingling of fluid from the separate formations.

in Figs. XIV and XV is shown a modified form of valve mandrel mounted in conjunction with atypical cross-over mandrel 20 for mounting the pressure loaded valvev for injection of gas under'pressureinto. theinner eductor 31.

The modified valve, mandrel is indicated generally at 163, and has a mashed-in portion 164, so ,thatthe .valve 30 may be recessed with respect to the outer diameter of the tubing string 5. The mandrel 163 is attached as a part of thetubing string 5 by means of a suitable coupling (not shown) and has extending therethrough' the eductor-tube 31. Themandrel -163-is threadedly engaged at its lower end with the typical cross-over mandrel'20 by means ofthreads indicated at 162.

A mounting lug 165 extends outwardly from themanmounting base 167 is attached to, and extends outwardly from, the valve mandrel 163, such base having a longitudinal passage 16S extending therethrough. The base 119 of'the valve 3i is threadedly engaged in the mounting base 167, as indicated at 169. An elongated conduit 170 is secured in the lower end of the mounting base 167 and is arranged to communicate with the passage 168. The conduit 170 extends downwardly and is secured in the upwardly facing receptacle 171, and is arranged to communicate with the lateral flow passage 172 passing through the wall of the typical crossover mandrel '20, so as to communicate with the inner bore of the crossover mandrel 20.

The modified valve mandrel 163 is particularly useful in wells having small casing diameter wherein there is insuflicient space for mounting the valve 30 on the outer side of the cross-over mandrel 29, as was the case in the form shown in Fig. VIII.

The construction of the cross-over mandrel 2t? and the slip joints 28 and 32 shown in Fig. XV are the same as already described; and like numerals have been employed for the parts thereof. Also, the flow valve 30 shown in Fig. XIV is the same in construction and operation as the typical flow valve already described.

Fig. XVI illustrates the detailedconstiuction of the through-flow fitting 90 shown diagrammatically in Figs. IV and XVII. InPig. XVI a suitable coupling 173 attaches the through-flow fitting 9d with the tubing string 5, said coupling being threadedly engaged with the fitting 9t by threads indicated at 174. The slip joint 95'is the same in construction as the slip joints already described, so that it is not deemed necessary to further describe same, other than to say that it is frictionally engaged in the slip joint receptacle 93, and is limited in its downward movement in the slip joint receptacle by engage-' ment of the beveled shoulder 137 on the head 136 with the beveled shoulder 175 in the slip joint receptacle 93. It will be seen that fluid may flow from the formation it) through the passageway 92 and connector pipe 94 into the eductor tube 31, and that fluid may flow through the lateral perforations 97 from the productive forma-' tion 3, into the tubing eductor 5. The sealing elements 14-1 on the slip joint 95 prevent the intermixture of fluids from the separate formations. The partition 91, shown diagrammatically in Fig. IV, is actually the thickened wall of the through flow fitting 96 which wall forms-the receptacle 93 for the slip joint 95. Fluid may not flow vabout the slip joint from. lower Zone 14 into the tubing. eductor 5.

Fig. XVII is a diagrammatic view of another form of installation of our multiple completion gas lift system wherein a well is completed in three zones,tone of which Zones 200 produces gas in sufficient volume and pressure to provide a supply of gas for the gas lifting of the other two zones 3 and 10. The zone 259 communicates with the interior of the casing 2 through the perforations- 201. The downnole equipment for producing the lower zones3 and 19 is the same inconstruction and operation communicates witha source of gas under pressure (not shown), is provided for the purpose of injecting gas into the casing for the purpose of unloading the well of fluid. Flow through the injection line 179 is Controlled by manually operated valve 188. p

A by-pass line 181 is arranged between the production line 178 and the injection line 179, flow through such line 181 being controlled by a manually operated valve 182.

A by-pass line 183 is arranged between the casing annulus 7 and the production line 177. p

A push down to open motor valve 184 is positioned in the line 176, such valve having a diaphragm 185 controlling the operation of the valve member therein, and a conventional control device 186 is arranged in conjunction therewith for controlling the movement of the diaphragm 185.

A push down to open motor valve 187 is arranged in the production line 177 to control the flow therethrough, the valve member in such motor valve being actuated by a suitable diaphragm 188.

A push down to close motor valve 189 is arranged in the by-pass line 183, such motor valve having a suitable diaphragm 190 controlling the movement of the valve member therein.

A manifolded control line 191 communicates with the control 186 and with the upper sides of the diaphragms 185, 188 and 198 of the motor valves 184, 187 and 189, respectively, so that the said motor valves areactuated simultaneously by the common control device 186, whereby when motor valve 189 is opened motor valves 184 and 187 are closed, and vice versa.

A push down to open motor valve 192 is connected in the line 176, the valve member in said motor valve being controlled by a diaphragm 193, and a time control device 194 controls the movement of said diaphragm. Another push down to open" motor valve 195 is mounted in the line 176, said motor valve being controlled by a diaphragm 196 through a control device 197. The control device 197 is so set, in a manner well known in the art, that the motor valve 195 will act as a regulator or relief valve in order to maintain a constant pressure on the casing annulus 7, such valve being arranged to permit the pressure in the casing to bleed off above a predetermined maximum pressure through line 176.

This invention will be more readily understood by considering the installation, operation and function of the several forms of installations disclosed herein.

One of the chief advantages of this invention is the provision of a combination of equipment which may be installed in the well with a minimum of time, inconvenience and danger, and the reduction of the number of parts and makeup joints required in completing a well for gas lift production from multiple zones of production.

The ease, economy and quickness of installation of the equipment employed in carrying out our invention may be illustrated by referring to the form of installation shown in Fig. I.

In making the installation shown in Fig. I, that portion of the tubing string 5, with the packer 9 and the tail pipe 12 mounted thereon, necessary to reach from the lower zone of production to the predetermined location of the cross-over nipple 16, is run into the casing. The cross-over nipple 16 is then attached as a part of the tubing string thus run, and suflicient number of joints of tubing are added and run into the casing to extend upwardly from cross-over nipple 16 to the predetermined location of the cross-over mandrel 20. This last section of tubing has the packer 8 incorporated therein at the proper spaced position. The section of tubing thus run into the hole, together with the parts thereof mentioned above, are supported at the well head by means of suitable slips as the tubing string is progressively made up and run into the casing, in a manner well known in the art.

The locations and spacing of the various parts of the tubing string thus run into the hole are determined by 14 consideration of the depths and spacing of the separate zones of production, and upon the producing characteristics of the particular zones. t

The section of pipe 26 is then run into the poi-tion of the tubing string already positioned in the casing and the slip joint 27 is inserted in the slip joint receptacle 17 at the upper end of the cross-over nipple 16. The crossover mandrel 20 is then attached to the section of the tubing string in the casing, and at the time of such connection the slip joint 28 on the pipe 26 is inserted in the slip joint receptacle 21. The flow valve 30 is then attached to the base 29 on the outer side of the crossover mandrel 20.

The remainder of the tubing string 5 is then made up by joining successive sections of tubing as the tubing string is progressively lowered in the casing. As the tubing string is made up and lowered into the casing the flow valves 40 and check valves 41, together with their respective mandrels, are placed in the tubing string in the proper spaced relationship. The tubing string 5, with the equipment incorporated therein, as described above, is landed and the packers 8 and 9 are set and the well head is attached at the upper end of the casing.

The eductor tube 31, which usually consists of a plurality of sections joined together, is then made up and progressively run into the tubing string 5. The lower most section of the eductor tube 31 has a slip joint 32 secured thereto which slip joint is landed and inserted in the upwardly facing slip joint receptacle 22 in the cross-over mandrel 20. The eductor tube 31 is supported on the well head by the head nipple 33.

The down-hole equipment has thus been run and placed in the casing with a minimum number of makeup joints and with only one flow valve communicating with the interior eductor 31, resulting in economy of installation and the elimination of future trouble from complicated down-hole installations such as has been practiced heretofore.

After the tubing string 5, with the various appurtenances attached thereto, and the eductor tube 31 are thus run and positioned in the casing, the surface connections are made from the well head to the injection gas supply line 60 and to the separators 37 and 48, with the various controls, valves and meters mounted in conjunction therewith, in manner familiar to those skilled in the art. The well is then ready to be placed on production.

After the well is put on production, fluids from the separate zones of production may then be gas lifted under exact control and the separate zones are segregated so that the fluids therefrom may not intermix.

After the installation has been so completed, the well is then ready for kicking-off or unloading.

It is the practice in the industry to fill the well with liquid, which may consist of natural fluids from the well, salt water, dead oil or mud, in order to hold the pressure existent in the producing formations of the well under control while the well is being worked over or prior to putting it on production. The level of such liquid ordinarily stands near the surface of the earth. In any event, the pressure head of such fluid must be greater than the pressure of the producing formations in order to confine such formation pressures.

In order to bring the producing formations into production by gas lift, the liquid must be removed from the well. Such removal of liquids is generally referred to as unloading the well.

The well is unloaded by the installation shown in Fig. I in the following manner:

Motor valve 62 is opened by control 64 and gas pressure is applied through the injection line 60 to the casing annulus 7. As such time the valve 36 is open and the valve 39 is closed. Motor valves 67 and 46 are closed and motor valve 50 is open, since the motor valves 67, 46 and 50 are simultaneously controlled by the common control 69. Motor valves 46 and 67 are push-down to V 7 15 close valves andmotor valve 54) is a push-down to open valve, so that when motor valves 46 and 67 are closed, motor valve 50 is open.

The series of tubing string flow valves 44) are so charged and spaced that they will be open under the pressure of the liquid head extending above the valves, combined with the gas pressure applied through the injection line 60. Therefore, with communication established through the flow valves from the casing annulus 7 into the tubing string 5, the injected gas pressure will cause the liquid in the casing annulus 7 to flow through the flow valves 44) into the tubing string and to the surface and outwardly through the open valve 50.

At or above the depth at which this flow will be stymied or stopped by the fluid head in the tubing balancing the gas pressure in the casing annulus, the uppermost tubing flow valve 40 is positioned. When the level of the liquid in the casing annulus has been lowered to the uppermost tubingflow valve 40, gas will be injected into the tubing through such valve and such gas will lift the liquid from the casing annulus through the lower tubing flow valves it). As the liquid level is lowered, the tubing flow valves 40 are successively uncovered, injecting gas into thetubing through such valves and lifting the liquid through the tubing to the surface until the lowermost tubing flow valve 40 is uncovered and exposed for action to the injected gas in the casing annulus. The lowermost tubing flow valve 40 is the production valve for the tubing educator 5.

While the liquid in the casingannulus 7 has been thus removed, the liquid in the inner eductor 31 has'beenj also removed. As mentioned above, the valve 39 in the flow line 38 is closed, and the valve 36 in the by-pass line .35 is open. Thus, the gas pressure applied to the casing annulus 7 has also been applied to the liquid column in the eductor tube 31 through by-pass line 35. The pressure charge in the inner eductor flow valve 3%) is so,set that suchvalve is opened by the injected gas pressure and the fluid head pressure in the eductor tube 31, so that during the unloading operation, the liquid in the eductor tube 31 flows downwardly through valve 30 in reverse direction to normal upward flow and outwardly into the casing annulus 7. The level of liquid in the eductor tube 31 is lowered at the same rate as the level of the liquid in the casing annulus 7, such liquid being transferred from the eductor tube 31 through the flow. valve 39 into the casing annulus 7, and such liquid will intermingle with the liquid in the casing annulus and flow through the tubing flow valves 46 into the tubing string 5 and by gas'lift' to the surface. Thus, the casing annulus, tubing annulus and the inner eductor. may be unloaded of liquid by the use of one conventional string of flow valves on the tubing and a single flow valve communicating with the inner eductor 31. The liquid is unloaded through a single eductor.

After the level of the liquid in the casing annulus 7 has been lowered to the lowermost valve in'the tubing string and the liquid in the inner eductor 31 has been lowered to approximately the same level, the well can then be placedon production in the following manner:

Still referring to Fig. I, valve 36 is closed and valve 39 is opened. The lower zone control 64 and the upper zone control 69 are adjusted to control the respective motor valves controlled thereby for the injection of gas into the casing annulus at the selected intervals, in accordance with the producing characteristics of the respective zon'esof production.

The controls 64 and 69 (and all other controls referred to herein) are commercial devices of conventional construction. They may be manually operated or actuated automatically by a change in pressure applied thereto or by a clock mechanism which is set to actuate the control at pre-selec'ted timed intervals. in any event, when such a control is actuated, gas pressure is admitted therethroughtothe upper face of thediaphragm of the motor" 16 I valve which it controls to open or close themotor valve. Several types of such controls are now available to the rade, the construction and operation of which are well known to those skilled in the art. It is not believed necessary to illustrate them in detail.

For the purpose of this explanation of operation and function, time controlled intervals of injection will be assumed.

Assuming that the producing characteristics of the lower Zone 10 is such that relatively frequent injections of gas are necessary to produce the allowable for such zone, then the lower zone control 64 would be set to' intermit by time control at such frequency. 1f the producing characteristics of the upper zone 3 were suchthat relatively infrequent gas injection were required, the upper zone control 69 would be set to intermit by time control at the desired frequency of injection. However, the time controls 64 and 69 would be so set as to inject gas for the upper zone between two of the more frequent injections for the lower zone.

The pressure charges in the tubing flow valves 40 are customarily arranged with the valve having the highest pressure charge being the uppermost valve and the succeeding valves down the tubing are charged at succeedingly lesser charges.

The fiow valve 34 has an opening pressure somewhat above the opening pressure of flow valve 40, and consequently the opening pressure of the valve 30 is somewhat higher than the opening pressure of the lowermost or workingvalve 40 on the tubing string. Therefore, any injected pressure necessary to open the lowermost valve 40 would be below the opening pressure of the valve 30. This permits the tubing string eductor 5 to be produced by gas lift independently of the inner eductor string 31.

At the predetermined interval for injection of gas into the eductor tube 31, the upper zone control 69 opens the motor valve 67, and simultaneously opens motor valve 46 and closes motor valve 56) through the common control line 71. With the by-pass line 45 open through motor valve 46, and the valve 36 closed and valve 39 open, the gas injected through motor valve 67 increases the pressure in the casing annulus 7 to the opening pressure of the how valve 30, thus injecting gas into the eductor 31 and lifting fluid in the eductor 31 andcausing it to flow through open valve 39 to the separator 37. At the same time all of the tubing flow valves 40 are also open, but since the interior of the tubing string 5 has been back-pressured through the open motor valve 46 and against the closed motor valve 50 with the same pressure as is present in the casing annulus 7, no gas can be injected through the valves 40 into the tubing, the pressure being equalized on the inside and outside of the tubing. In the event there is liquid present in the tubing string 5'above any of the tubing flow valves 40, the back flow check valves 41 will prevent the passage of such liquid from the tubing 5 into the casing annulus 7. Therefore, commingling of fluids from the separate zones of production is rendered impossible.

At the end of the selected time interval for the injection of gas into the eductor 31, the upper zone control 69 closes the motor valves 67 and 46, simultaneously opening motor valve 50. Gas injectionisprecluded, all flow valves 36 and 40 close, and the well is ready for the more frequent injection of gas into the casing annulus 7 by the lower zone control 64 for producing fluid by gas lift from the lower zone ltlthrough the tubing eductor 5. The lower zone control 64 intermittently opens the motor valve 62, allowing gas to be injected into the casing annulus 7 and the pressure is built up inthe casing annulus to the opening pressure of the lowermost tubing flow valve 40, thus injecting gas into the tubing for the lifting of fluid therein. The fluid flows outwardly through the; open valve 50 into the separator 48. Since upper zonefiow valve 36 has an opening pressure'higher' 17 than the lowermost working valve 40, no gas will be injected into eductor 31 during this cycle.

It is to be noted that the gas injected to produce each zone is measured and recorded separately by the meters 65 and 70 for the respective zones, and that the sum of the injected gas and formation gas produced from each zone is likewise measured and recorded by the meters 54 and 57 for the respective zones. Furthermore, since the flow valves used to produce each zone are controlled wholly from the surface, accurate and exact control of the amount of gas injected necessary for the production of each zone, and the frequency of injection for each zone may be set and adjusted to meet the changing con ditions of the productive formations and to accurately produce each zone in conformity with the allowable production thereof.

In Fig. I it is assumed that the upper zone of produc tion 3 is the stronger of the two productive zones, requiring less frequent gas injection, and the inner eductor 31 is thus placed in communication with such zone. Since valve 30 opens at a higher pressure than working valve 40 it is desirable to operate valve 30 less frequently than valve 40 in the interest of conservation of gas. However, it will be readily understood that the system will operate satisfactorily with the valves 30 and 40 reversed in their communication with the respective zones.

It may occur that the lower zone of production 10 is the stronger and has the higher productive characteristics, and it thus may be desirable to place the inner eductor 31 and flow valve 30 in communication with the lower zone. Fig. IV illustrates a down-hole installation in which the eductor 31, having the single flow valve 30 for injection of gas thereto, communicates with the lower zone of production 10 and the tubing string eductor 5 communicates with the upper zone.

The special through flow fitting 90, the construction of which has been heretofore described, is attached in the tubing string to allow fluid to flow therethrough into the inner eductor 31. The down-hole equipment in the modified form shown in Fig. IV is run into the hole in the same manner as was described above with reference toFig. I. Independence of the operation of the inner eductor valve 30 from the operation of the tubing production valve 40 is emphasized by the fact that, in Fig. IV, the cross-over mandrel 20 and valve 30 have been positioned at a relatively higher position along the tubing string than was the case in Fig. I. The mandrel 20 and flow valve 30 may be positioned at any point along the tubing string as required by the conditions in the well.

The surface equipment used in connection with the down-hole equipment shown in Fig. IV is the same as that shown in Fig. I and the operations of unloading and producing may be the same as described in connection with Fig. I, the more infrequent injections of gas being injected through the flow valve 30 into the eductor 31, between two more frequent injections through lowermost working valve 40 into the tubing string 5.

A condition which often occurs in a well is that in which one of the zones of production has high productivity characteristics and will normally flow without artificial assistance, but will occasionally become logged up due to presence of salt water or as the result of choking it down to comply with the maximum production allowable. It is, therefore, desirable to provide gas-lifting for such zone only when it becomes so logged up to clear the eductor and cause it to resume normal flow. Our gas lift system is particularly applicable to meet this condition, wherein the eductor 31 communicates with the stronger productive zone.

In order to meet the needs of such condition mentioned above, a further modification in the surface equipment could be made by providing a pressure actuated control 69 for the opening and closing of the motor valve 67 for controlling the injection of 6 gas to the eductor 31. Such control 69 could be actuated by a change in pressure at the wellhead in the eductor 31. The control 69 would be so adjusted that a predetermined drop in flowing pressure of the lower formation 10 betweenthe control 69 and the upper end of eductor 31 (transmitted through a suitable control line, not shown) would cause the motor valve 67 to be opened and gas would be injected through such motor valve into the casing annulus 7. In the event that the motor valve 62, through which gas is injected for operation of the lowermost tubing valve 40, would be open at that time no gas would be injected into the tubing annulus through the valve 40 because the tubing is backpressured through the open motor valve 46, the motor valve 50 being closed. This is so because the motor valves 67, 46 and 50 are interconnected by a common control line 71, and when motor valve 67 is open, motor valve 46 is open and motor valve 50 is closed. When motor valve 67 is opened, the pressure in the casing annulus would be built up to such an extent as to open the flow valve 30 and allow the injection of gas therethrough into the eductor 31.

After the eductor 31 has been unloaded and opened up by gas lift and normal flowing pressure is resumed from the formation with which it communicates, the control 69 would close the valve 67, close valve 46 and open valve 50 so that normal injection cycles could be resumed through the lower tubing valve 40. This modification would be applicable to both Fig. I and Fig. IV installations.

The modified installation shown in Fig. V has a downhole installation identical with that shown in Fig. I, except that a second cross-over mandrel 20a is added in the tubing string below the cross-over mandrel 20. It will be noted that a back-flow check valve is interposed between the flow valve 99 and the passage 98 into the inner eductor 31. A connector pipe 101, having slip joints on opposite ends inserted in the cross-over mandrels 20 and 20a is provided between the cross-over mandrels. The surface equipment is the same as in Fig. I except that a push down to close motor valve 102 is substituted for the manually operated valve 36 and a push down to open motor valve 103 is substituted for the manually operated valve 39. The diaphragm of the motor valves 62, 102 and 103 are interconnected by a common control line 104 for simultaneously actuating such motor valves by the common control 64.

The form of installation shown in Fig. V is especially applicable to installations in which the separate producing zones require substantially the same frequency of gas injection. Such an installation is also advantageous in wells with large casing diameters wherein the buildup of casing pressure to open the flow valve controlling gas injection into the inner eductor 31 would require an excessive amount of gas.

In such installation the flow valve 30 is used only in unloading the well of liquid. As in Fig. I the valve 30 is loaded to a pressure equal or above the pressure loading of the uppermost tubing valve 40.

In order to unload the well of liquid by use of the modification shown in Fig. V the motor valve 62 is opened by the control 64, which at the same time opens motor valve 102 and closes motor valve 103. The injected pressure is then applied through the injection line 60 to the casing annulus 7 and to the interior of the inner eductor 31 through the by-pass line 35. The pressure is built up in the casing annulus, and the same pressure is built up in the inner eductor 31 against the closed motor valve 103. At such time the motor valves 67 and 46 are closed and motor valve 50 is open, such valves being actuated by a common control 64, in the manner hereinbefore explained. When the pressure has built up in the casing annulus and in the inner eductor 31 to such a value as to open the valves 40 and. valve 30, the liquid in the inner eductor 31 is flowed in reverse direction and ejected through the valve 30 into the casing annulus 7 and the liquid in the casing annulus 7 is ejected through the valves un tin -1 46 into the tubing annulus. Such liquid is flowed out-w wardly through the open valve 51) to unload the well of liquid in the manner heretofore described in connection with Fig. I. At the end of the unloading cycle, gas injection stopped and all valves return to normal condition.

9 After the well has been unloaded of liquid to the desired level, the well is ready to be put on production in the following manner:

The flow valve 99 is an operating valve and is pressureloaded at substantially the same pressure as the lowermost tubing operating valve 40, and the valve 99 will be opened or closed at approximately the same time that the lower most tubing operating valve 40 is opened or closed.

The lower zone control 64 is so set at the time interval of injection selected as to simultaneously open the motor valves 62 and 102 and close motor valve 103. The casing. preesure rises to the opening pressures of flow valve lowermost working valve 40 and gas injection in-v to tubing eductor 5 occurs through the lowermost working valve 40, but injection into eductor 31 is prevented. Back pressure of the same value as the casing pressure is applied in eductor 31 through the open motor valve 102 against the closed motor valve 103, so that back flow check valve 100 prevents the injection of gas into the upper zone eductor 31.. Therefore, during the injection cycle for the lower zone 10, gas is injected only into the lower zone tubing eductor 5, and the fluid from the lower zone is gas lifted through the open valve 50.

When the injection cycle for the tubing eductor 5 is completed, gas injection is stopped, all flow valves are closed and motor valves '62, 67, 46 and 102 are closed and motor valves 50 and 103 are open, such valves then being in normal condition.

When gas injection is required into the upper zone eductor 31, at the time interval selected, the upper zone control 69 simultaneously opens motor valves '67 and 46 and closes motor valve 50. Pressure is built up in the casing annulus 7 to suflicient extent to open both the flow valve 99 and the lowermost working valve 40, but gas injection through the working valve 40 into the tubing aductor 5 is prevented by the back pressure in the tubingthrough the open motor valve 46 against' the closed motor valve 50, the injected pressure being applied and built up, simultaneously in both the casing annulus and tubing annulus. Therefore, gas is injected only into the upper zone eductor 31 during this cycle, and fluid is gas lifted from such eductor through open valve 103.

At the completion of the cycle of injection of gas into the inner eductor '31, as above described, all valves return to the normal position, described above, and no injection occurs into either the lower zone eductor 5 or the upper zone eductor 31.

During the injection of gas into each of the separate eductors 5 and '31, back flow of well fluids from the back pressured eductors into the casing annulus 7 is effectively blocked by the check valves 41 and 100, respectively, and since the opening pressure of both the flow valve 99. and the lowermost working flow valve 40 is substantially lower than the opening pressure of the unloading flow valve 30, the valve 30 is not open during either ofthe production cycles and no back flow check valve is required in connection with the valve 30.

Thecycles of gas injection for production through each zone eductor may be periodically repeated in the manner described as the condition of the separate formations mayv require. Exact adjustment and control at the surface. for gas injection and production for both zones may be carried out, at the same time permitting exact measurement of injected gas for each zone and production from each. zone.

The modification form shown in Fig. V affords the same advantages of simplicity-and economy of installation and of flexibility and adjustability as was described abovein. connection with Fig. I. i i i The modified form. of installation shown in Fig. XVlI 20 is applicable to a well wherein there is a third zone 200 which produces gas in sufllcient volume and pressure to gas lift the other zones 3 and 10, so that no outside source of gas is required for the production of fluid from the zones 3 and 10.

The down-hole installation shown in Fig. XVH is the same as that shown in Fig. IV, and previously described in connection therewith. The down-hole equipment could be arranged in accordance with either of the other forms of installations described above.

The arrangement of the surface control equipment has been modified.

For unloading the well of liquids in the form shown in Fig. XVII, the valve is opened and gas under pressure is injected from a suitable source into the easing annulus 7 through the injection line 179. At the same time valve 18; is opened thus equalizing the pro-.- sure between the casing annulus 7 and the inner eductor 31, the. valve 292 being left closed.

During the unloading stage motor valves 1854, 189, 192 and 195, are closed and motor valve 137 is open. Unloading gas is introduced into the casing annulus 7 and into eductor 3 1 through the injection line 179 and bypass line 131, and the pressure is built up to such extent as to open the flow valves '40 and 30. The liquid in the casing annulus 7 and in the eductor 31 are depressed and ejected out the well through the tubing 5. As in the installations shown in Figs. I and IV the liquid in the eductor '31 is flowed downward in reverse direction from normal upward flow through. the flow valve 30 into the casing annulus and the liquid is ejected from the casing annulus through the flow valves 40 into the tubing eductor 5. The liquid is flowed out of the tubing eductor through line =177 and open valve 187 until the Well is unloaded of liquid to the. desired level.

After the casing annulus 7 and eductor 31 have been cleared of liquid to the desired level all surface control valves are returned to normal condition, gas injection for unloading is stopped, and flow valves 30 and .43 are closed and the well is ready to be put on production as follows:

The gas from the upper zone 2% will, of course, be produced into the casing annulus 7, but will not escape from the casing annulus until the pressure thereof is built up to the predetermined value of' relief by the setting of the regulating motor valve 195. When this pressure has been reached motor valve wi1l open to allow surplusproduction of gas from zone 290 to flow through the flow line 176. and through motor valves 192 and 184, which motor valves are normally open. Such production of surplus gas will continue until time for the injection of gas for artificially lifting fluid from either or both of-the zones of production 3 and 1.9. The regulator motor valvemaintains a constant pressure in casing an nulus 7.

It will be assumedthat upper zone 3, which is produced by injection of gas through the lowermost tubing flow valve 40, is the zone requiring the most frequent injection of gas. When the preselected time for injection of gas for production of zone it arrives motor valve 192 will be closed by its control 194, the control 194 having been set to close and open valve 192 at timed intervals. Thereby the casing flow line 176 is closed. When motor valve 192 is closed the regulator valve 195 is rendered inoperative by reason of the fact that excess gas from zone 201 cannot pass through. closed valve 192 and through flow line 176. Thus the pressure in thecasing an nulus is allowed to rise to the opening pressure of the lowermost tubing operating valve. 40. Gas will be injected into the tubing 5 through working valve 40, which will result-in the gas lifting offluid fromzone 3 through flow line 177. Duringthis cycle motor valves 187 and 184 are open and motor valve 189 is closed, such being the normal condition of such valves.

At the end of the predetermined cycle for the production of fluid from zone 3 the control 194 for the motor valve 192 will cause said motor valve 192 to reopen and motor valve 195 will immediately resume its control over the pressure in the casing annulus 7, keeping such pressure below the opening pressure of the working valve 40 and the flow valve 30.

When the time arrives to inject gas into the eductor 31 (such time for injection being between two of the more frequent injections for the tubing eductor 5), the common control 186 for the motor valves 184, 187 and 139 will cause motor valve 184 to close. Simultaneously, motor valve 187 will close and motor valve 189 will open, the diaphragms for these last three named motor valves being actuated through a common control line 191 by the common control 186. When motor valve 184 is closed, motor valve 195 becomes inoperative to let off excess pressure in the casing annulus and the pressure in the casing annulus will increase to the opening pressure of valve 30. Since motor valve 189 is open and motor valve 187 is closed, the increased pressure in the casing annulus is also applied to the interior of the tubing 5 through by-pass line 183 and line 177 against closed valve 187. Injection of gas is prevented through the tubing flow valves 40 by thus back'pressuring the tubing at the same pressure as the casing pressure. The back-pressure check valves 41 prevent the flow of fluid from tubing 5 into casing annulus 7. The pressure is built up to such an extent in the casing annulus as to open the valve 30 and gas is injected into the eductor 31 and the gas lift cycle for the lower zone will occur. The production from the lower zone 10 flows through the open valve 202 in flow line 187. Valve 202 is normally left open and is closed only during the unloading operation. Valves 180 and 182 are normally left closed and are open only during the unloading operation.

At the end of the cycle of production through eductor 31 the control 186 for motor valve 184 causes motor valves 184, 187 and 189 to return to their normal position (valves 184 and 187 being open and valve 189 being closed), and the regulator motor valve 195 may resume its normal operation of bleeding off excess casing pressure above the predetermined maximum. The casing pressure will return to a pressure just under the closing pressure of the lowermost tubing valve 40, and will allow the production through line 176 of all gas from zone 200 over and above such predetermined pressure.

The above cycles of production are repeated at the intervals determined by the settings of the controls for the respective zones of production.

The modified installation shown in Fig. XVII affords all of the advantages from the standpoint of control and simplicity and economy of installation as that afforded by the other forms of installation heretofore described, and in addition provides an installation wherein gas from one of the productive zones in the well may be utilized in the gas lifting of fluids produced from other zones of production in the same well, yet with perfect control from the surface over said gas lifting.

In some wells one of the zones of production may be sufficiently strong to flow without the aid of gas lift during production, but it may be necessary to use artificial means to unload the eductor for such zone of liquid in order to bring it to a condition of natural flow. In such a situation the valve 30, with appurtenant controls and settings as described herein, could be employed solely for unloading the eductor for such zone of liquid and bringing such zone into production. Thereafter valve 30 could be maintained inoperative until such time as the zone has been depleted to such an extent as to require gas lift. The other zone would be gas lifted as usual. Thus the unloading operation has utility apart from the production operation. 1

It will be apparent that other and further forms for carrying out of our invention may be devised and still remain within the scope and spirit of the appended claims.

We claim:

1. A method of removing fluid by gas lift from a well having plural flow passages therein arranged to communicate with separate zones of production comprising the steps of, the reversal of the normal direction of flow in one of the flow passages, the forcing of fluid from such flow passage into a second flow passage, the forcing of fluid from the second flow passage into a third flow passage, and the displacement of fluid in the third flow passage by gas lift to the earths surface.

2. A method of removing fluid by gas lift from a well having plural flow passages therein arranged to communicate with separate zones of production comprising the steps of, the reversal of the normal direction of flow in one of the flow passages, the forcing of fluid from such flow passage into a second flow passage, the forcing of fluid from the second flow passage into a third flow passage, the displacement of fluid in the third flow passage by gas lift to the earths surface, the application of a common gas pressure to two of the flow passages, and the injection of gas from one of said last-named flow passages into the first-named flow passage.

3. A method of removing fluid by gas lift from a well having separate zones of production wherein there is a well casing and an eductor passage communicating with each zone of production extending into the casing comprising the steps of, applying a common gas pressure to the annular space between the well casing and the eductor passages for the separate zones and to the eductor passage communicating with one of the zones of production, the forcing of fluid from said eductor passage into the said annular space, the forcing of fluid from the said annular space into another eductor passage, the displacement of fluid by gas lift from the last-named eductor pas sage to the earths surface, the release of gas pressure from the first-named eductor passage, the application of a common gas pressure to the second-named eductor passage and to the said annular space, and the injection of gas from the annular space into the first-named eductor passage.

4. A method of removing fluid by gas lift from a well having separate zones of production, wherein there is a well casing and an eductor passage communicating with each zone of production extending into the casing comprising the steps of, applying a common gas pressure to the annular space between the well casing and the eductor passages for the separate zones and to the eductor passage communicating with one of the zones, the forcing of fluid from the said eductor passage into the said annular space, the forcing of fluid from the said annular space into another eductor passage, the displacement of fluid by gas lift from the last-named eductor passage to the earths surface, the release of pressure from the first-named eductor passage, the application of a common gas pressure to the second-named eductor and to the said annular space, the injection of gas from the annular space into the first-named eductor passage, the release of pressure from the second-named eductor, the lowering of the gas pressure in the annular space, and the injection of gas from the annular space into the second-named eductor passage at such lowered pressure.

5. A method of lifting fluid by gas lift from a well having plural zones of production wherein there is a well casing, each zone of production having a separate eductor passage extending into the well casing and communicating therewith comprising the steps of, forcing fluid from one of the eductor passages into the annular space between the well casing and the eductor passages, the forcing of fluid from the annular space into the other eductor passage, and the displacement of fluid through the secondnamed eductor by gas lift to the earths surface.

6. A method of lifting fluid by gas lift from a Well having plural zones of production wherein there is a well casing, each zone of production having a separate eductor passage extending into the casing and communicating therewith comprising the steps of, forcing fluid from one of the eductor passages into the annular space between the well casing and the eductor passages, the forcing of fluid from the annular space into the other eductor passage, and the displacement of fluid through the secondnamed eductor passage by gas lift to the earths surface, the fluid being forced from the first-named eductor passage and from the annular passage simultaneously by a common gas pressure applied thereto.

7. A method of lifting fluid by gas lift from a well. having plural zones of production wherein there is a well casing, each zone of production having a separate eductor passage extending into the casing and communicating therewith comprising the steps of, forcing fluid from one of the eductor passages into the annular space between the well casing and the eductor passages, the forcing of fluid from the annular space into the other eductor passage, the displacement of fluid through the second-named eduetor passage by gas lift to the earths surface, the release of force applied to the first-named eductor passage, the application of a common gas pressure to the annular space and to the second-named eductor passage, and the injection of gas from the annular space into the first-named eductor.

8. A method of lifting fluid by gas lift from a Well having plural zones of production wherein there is a well casing, each zone of production having a separate eductor passage extending into the casing and communieating therewith comprising the steps of, forcing fluid from one of the eductor passages into the annular space between the well casing and the eductor passages, the forcing of fluid from the annular space into the other eductor passage, the displacement of fluid through the second-named eductor passage by gas lift to the earths surface, the release of the force applied to the firstnamed; eductor passage, the application of a common gas pressure to the annular space and to the second-named eductor; passage, the injection of gas from the annular space into the first-named eductor passage, the discontinuance of injection of gas into the first-named eductor passage, the release of the gas pressure applied to the second-named eductor passage, and the injection of gas from the annular space into the second-named eductor passage.

9. A method of lifting fluid by gas lift from a well having plural zones of production wherein there is a Well casing, each zone of production having a separate eductor passage extending into the casing and communieating therewith comprising the steps of, forcing fluid from one of the eductor passages into the annular space between the well casing and the eductor passages, the forcing of fluid from the annular space into the other eductor passage, the displacement of fluid through the second-named eductor passage by gas lift to the earths surface, the release of the force applied to first-named eductor'passage, the application of a common gas pressure to the annular space and to the second-named eductor passage, the injection of gas from the annular space into the first-named eductor passage, the discontinuance of injection of gas into the first-named eductor passage, the release of the gas pressure applied to the second-named eductor passage, and the injection of gas from the annular space into the second-named eductor passage, the injected gas to each said eductor passage being supplied through a separate supply passage, Whereby the gas injected into each eductor passage may be measured.

10. A method of placing and maintaining on production a well having separate zones of production with a well casing'and an eductor passage communicating with each zone and extending into the casing comprising the steps of, reversing the normal direction of flow in one eductor passage, the forcing of fluid from said eductor passage into the annular space between the well casing and the eductor passages, the forcing of fluid from the annular space into another eductor passage, the displacement of fluid in the second-named eductor passage by gas lift to the earths surface until the well is unloaded of fluid to a desired level, ceasing the unloading of the Well of fluid, the application of a common gas pressure to the annular space and to one of the eductor passages, and the injection of gas from the annular space into another eductor passage while the said eductor passage is so maintained under pressure.

11. A method of placing and maintaining on production a well having separate zones of production with a well casing and an eductor passage communicating with each zone and extending into the casing, comprising the steps of reversing the normal direction offlow in one eductor passage, the forcing of fluid from said eductor passage into the annular space between the well casing and the eductor passages, the forcing of; fluid from the annular space into another eductor passage, the displacement of the fluid in the second-named eductor passage by gas lift to the earths surface until the well is unloaded of fluid to the desired level, ceasing the unloading of the well, the application of a common gas pressure to the annular space and to one of the eductor passages, the injection of gas from the annular space into another eductor passage while the said eductor passage is so maintained under pressure, the release of gas pressure from the said eductor passage, ceasing the in jcction of gas into the said another eductor passage, and the injection of gas from the annular space into the eductor passage from which the gas pressure has been so released.

12. A method of gas lifting fluids from a well having separate zones of production, each zone of production naving a well casing therein and a separate eductor passage communicating therewith and extending into the casing comprising the steps of, placing the eductor passages in communication, the introduction of gas pressure to the annular space between the eductor passages and the Well casing, the application of such gas pressure to one of the eductor passages, the forcing of fluid by such gas pressure from the last-named eductor into the annular space, the forcing of fluid from the annular space into another eductor passage, and the displacement of the fluid in the said another eductor passage by gas lift to the earths surace until the well is unloaded of fluid to a desired level.

13. A method of gas lifting fluid from a well having separate zones of production, wherein there is a well casing and a separate eductor passage extending into the casing communicating with each zone of production comprising the steps of, forcing fluid from one eductor pas sage into the annular space between the well casing and the eductor passages, the forcing of fluid from the annular space into another eductor passage, the continued application of such force until the well is unloaded of fluid to a desired level through the second-named eductor passage, and thereafter alternately injecting gas under pressure from the annular space into the columns of fluid in each eductor passage.

14. A method of gas lifting fluid from a well having separate zones of production, wherein there is a well casing and a separate eductor passage extending into the well casing communicating with each zone of production comprising the steps of, forcing fluid from one eductor passage into the annular space between the Well casing and the eductor passages, the forcing of fluid from the annular space into another eductor passage, the continued application of such force until the well is unloaded offluid to a desired level through the second-named eductor passage, the application of a common gas pressure to the second-named eductor passage and to the annular space, the injection of gas from the annular space into a column of fluid in the first-named eductor passage, the discontinuance of such gas injection into the firstnamed eductor passage, the injection of gas under pres- 25 sure through another supplypassage into the annular space, and the injection of gas from the annular space into a column of fluid in the second-named eductor passage.

15. A method of gas lifting fluid from a well having separate zones of production wherein there is a well casing and a separate eductor passage extending into the casing communicating with each zone of production comprising the steps of, forcing fluid from one eductor passage into the annular space between the well casing and the eductor passages, the forcing of fluid from the annular space into another eductor passage, the continued application of such force until the well is unloaded of fluid to a desired level through the second-named eductor passage, the application of a common gas pressure to the second-named eductor passage and to the annular space, the injection of gas from the annular space into a column of fluid in the first-named eductor passage, the discontinuance of such gas injection into the first-named eductor passage, the injection of gas under pressure through another supply passage into the annular space, the injection of gas from the annular space into a column of fluid in the second-named eductor passage, the pressure of the gas injected into the first-named eductor passage being higher than the pressure of the gas injected into the second-named eductor passage.

16. A method of gas lifting fluid from a well having separate zones of production wherein there is a well casing and a separate eductor passage extending into the casing communicating with each zone of production comprising the steps of, forcing fluid from one eductor passage into the annular space between the well casing and the eductor passages, the forcing of fluid from the annular space into another eductor passage, the continued application of such force until the well is unloaded of fluid to a desired level through the second-named eductor passage, the application of a common gas pressure to the second-named eductor passage and to the annular space, the injection of gas from the annular space into a column of fluid in the first-named eductor passage, the discontinuance of such injection into the first-named eductor passage, the injection of gas under pressure through another supply passage into the annular space, the injection of gas from the casing annulus into a column of fluid in the second-named eductor passage, the gas being injected into each eductor passage at substantially the same pressure.

17. A method of gas lifting fluid from a well having separate zones of production comprising the steps of, placing the zones of production in communication to unload the well of fluid, separating the zones, and the injection of gas under pressure to each zone at separate intervals of time.

18. A method of gas lifting fluid from a well having' separate zones of production comprising the steps of, placing the zones of production in communication to unload the well of fluid, separating the zones, the injection of gas under pressure to each zone at separate intervals of time, the injection of gas to each zone being through a separate supply passage.

19. A method of gas lifting fluid froma well having separate zones of production, comprising the steps of, placing the zones of production in communication to unload the well of fluid, separating the zones, the injection of gas under pressure to each zone at separate intervals of time, the injection of gas to each zone being through a separate supply passage, and the gas injected into one zone being at a higher pressure than the pres sure of gas injected into another zone.

20. A method of gas lifting fluid from a well having separate zones of production comprising the steps of, placing the zones of production in communication to unload the well of fluid, separating the zones, the injection of gas under pressure to each zone at separate intervals of time, the injection of gas to each zone being through a separate supply passage, the gas injected into one zone being at a higher pressure than the pressure of gas injected into another zone, and measuring the gas injected to each zone.

21. A method of gas lifting fluid from a well having separate zones of production, comprising the steps of placing the zones of production in communication to unload the well of fluid, separating the zones, the injection of gas under pressure to each zone at separate intervals of time, the injection of gas to each zone being through a separate supply passage, the gas injected into one zone being at a higher pressure than the pressure of gas injected into another zone, measuring the gas injected to each zone, and measuring the gas produced from each separate zone.

22. A method of producing fluid by gas lifted from separate zones of production in a well wherein there is a separate eductor passage communicating with each zone of production comprising the steps or, applying a common gas pressure to the annular space between the well casing and the eductor passages and to one of the eductor passages, the injection of gas from the annular space into another eductor passage; the release of gas pressure from the first-named eductor passage, and the injection of gas from the annular space into the first-named eductor passage.

23. A method of producing fluid by gas lift from separate zones of production in a well wherein there is a separate eductor passage communicating with each zone of production comprising the steps of, applying a common gas pressure to the annular space between the well casing and said eductor passages and to one of the eductor passages, the injection of gas from the annular space into another eductor passage, the .release of gas pressure from the first-named eductor passage, the application of a common gas pressure to the annular space and to the second-named eductor passage, and the injection of gas from the annular space into the first-named eductor pas-,

sage.

24. A method of producing fluid from separate zones of production in a well wherein there is a separate eductor passage communicating with each zone of production, one of which zones of production produces gas into one of the eductor passages in suflicient quantity and pressure to gas lift fluids fromthe other zones of production comprising the steps of, confining the pressure in the firstnamed eductor passage at a predetermined level, the raising of the pressure in the first-named eductor passage above the predetermined level, the injection of gas from such eductor passage into a second eductor passage, the reduction of the pressure in the first-named eductor passage to the predetermined level, the discontinuance of injection of gas into the second-named eductor passage simultaneously with such reduction of pressure in the first named eductor passage, the raising of the pressure in the first-named eductor passage above the predetermined level; the application of such increased pressure to the second-named eductor passage, and the injection of gas from the first-named eductor passage into a third eductor passage.

25. A system of gas lifting fluid from a well having separate zones of production comprising, a well casing; a tubing eductor arranged within the casing communicating with one zone of production through perforations in the wall of the casing; packer means between the tubing eductor and well casing for separating the zones; a plurality of pressure-operated flow valves spaced along the tubing eductor and arranged to communicate therewith; an eductor tube arranged in the casing communicating with another zone, of production through perforations in the wall of the casing; packer means between the tubing eductor and eductor tube for separating one from the other; a pressure-operated flow valve arranged to communicate with the eductor tube, the said valve having an opening pressure at least equal to the opening pressure of the topmost flow valve on the tubing eductor; means to admit gas under pressure to the casing and to the eductor tube suflicient to open the flow valves and to force fluid from the eductor tube into the casing and to force fluid from the easing into the tubing eductor to thereby unload the well of fluid though the tubing eductor; means for applying a common gas pressure to the casing and to the tubing eductor, said common gas pressure being suflicient to open the flow valve on the eductor tube to inject into the eductor tube; and means for applying gas pressure to the casing suflicient to open the lowermost valve on the tubing eductor to inject gas under pressure into the tubing eductor.

26. A system of gaslifting fluid from a well having separate zones of production comprising, a well casing; a tubing eductor arranged within the casing communicating with one zone of production through perfora tions in the Wall of the casing; packer means between the tubing eductor and well casing for separating the zones; a plurality of pressure operated flow valves spaced along the tubing arranged to communicate therewith; an eductor tube arranged within the tubing eductor communicating with another zone of production through perforations in the wall of the casing; packer means between the tubing eductor and eductor tube for separating one from the other; a pressure operated flow valve mounted on the tubing eductor and arranged to communicate with the eductor tube, the said valve having an opening pressure at least equal to the opening pressure of the topmost flow valve on the tubing eductor; means to admit gas under pressure to the casing and to the eductor tube suflicient to open the flow valves to force fluid from the eductor tube into the casing and to force fluid from the casing annulus into the tubing eductor to thereby unload the well of fluid through the tubing eductor; means for applying a common gas pressure to the casing and to the tubing eductor, said common gas pressure being suflicient to open the flow valve communicating with the eductor tube to inject gas into said eductor tube; and means for supplying gas pressure to the casing suflicient to open the lowermost valve communicating with the tubing eductor to inject gas under pressure into the tubing eductor.

27. A system of gas lifting fluid from a well having separate zones of production comprising, a well casing; 21 tubing eductor arranged within the casing communicating with one zone of production through perforations in the wall of the casing; packer means between the tubing eductor and well casing for separating the zones;

a plurality of pressure operated flow valves spaced along the tubing arranged to communicate therewith; an eductor tube arranged within the tubing eductor communicating with another zone of production through perforations in the wall of the casing; packer means between the tubing eductor and eductor tube for separating one from the other; a pressure operated flow valve mounted on the tubing eductor and arranged to communicate with the eductor tube, the said valve having an opening pres sure at least equal to the opening pressure of the topmost flow valve on the tubing eductor; means to admit gas under pressure to the casing and to the eductor tube sufficient to open the flow valves to force fluids from the eductor tube into the casing and to force fluid from the casing into the tubing eductor to thereby unload the well of fluid through the tubing eductor; means for applying a common gas pressure to the casing. and to the tubing eductor, said common gas presure being suflicient to open the flow valve communicating with the eductor tube to inject gas into said eductor tube; means for supplying gas pressure to the casing suflicient to open the lowermost valve communicating with the tubing eductor to inject gas under pressure into the tubing eductor, and a back flow check valve mounted between each of the flowvalves communicating with 28 the tubing eductor and the interior of the said eductor to prevent the flow of fluid from the tubing eductor into the casing while gas is being injected into the;

eductor tube. r

28. A system of gas lifting fluid from a Well having separate zones of production comprising, a well casing; 21 tubing eductor arranged within the casing communicating with one zone of production through perforations in the Wall of the casing; packer means between the tubing eductor and well casing for separating the zones; a plurality of pressure operated flow valves spaced along the tubing arranged to communicate therewith; an eductor tube arranged within the, tubing eductor communicating with another zone of production through perforations in the wall of the casing; packer means between the tubing eductor and eductor tube for separating one from the other; a pressure operated flow valve mounted on the tubing eductor and arranged to communicate with the eductor tube, the said valve having an opening pressure at least equal to the opening pressure of the topmost valve on the tubing eductor; means to admit gas under pressure to the casing and to the eductor tube sufli cient to open the flow valves to force fluids from the eductor tube into the casing and to force fluid from the casing into the tubing eductor to thereby unload the well of fluid through the tubing eductor; means for applying a common gas pressure to the casing and to the tubing eductor, said common gas pressure being suflicient to open the flow valve communicating with the eductor tube to inject gas into said eductor tube; means for applying gas pressure to the casing suflicient to open the lowermost valve communicating with the tubing eductor to inject gas under pressure into the tubing eductor; a back flow check valve mounted between each of the flow valves communicating with the tubing eductor and the interior of the said eductor to prevent the flow of fluid from the tubing eductor into the casing while gas is being injected into the eductor tube; the injection of gas for each of said eductors being supplied to the casing through a separate conduit whereby the injected gas to each eductor may be measured.

29. A system of gas lifting fluid from a well having separate zones of production comprising, a well casing; 21 tubing eductor arranged within the casing communicating with one zone of production through perforations in the wall of the casing; packer means between the tubing eductor and well casing for separating the zones; a plur-ality of pressure operated flow valves spaced along the tubing eductor arranged to communicate therewith; a back flow check valve arranged between each of the said flow valves and the interior of the tubing eductor to prevent the flow of fluid from the tubing eductor into the casing; an eductor tube arranged in the tubing eductor communicating with another zone of production through perforations in the wall of the casing; packer means between the tubing eductor and eductor tube for separating one from the other; a pressure operated flow valve mounted on the tubing eductor and arranged to communicate with the eductor tube, the said flow valve having an opening pressure at least equal to the opening pressure of the topmost flow valve on the tubing eductor; means to admit gas under pressure to the casing and to the eductor tube sulficient to open the flow valves to force fluid from the eductor tube into the casing and to force fluid from the casing into the tubing eductor to thereby unload the well of fluid through the tubing eductor; a second pressure operated flow valve mounted on the tubing eductor and arranged to communicate with the eductor tube; a back flow check valve arranged between said second flow valve and the interior of the eductor tube to prevent the baclc flow of fluid from the eductor tube into the casing said second flow valve having an opening pressure substantially the same as the opening pressure of the lowermost flow valve communi- 

